1. Field of the Invention
The present invention generally relates to structures and assemblies for use in connection with a patient interface device, such as a respiratory mask, and a mask attachment assembly, such as headgear having straps to retain the mask in a sealed position on a user's face. In particular, the present invention is related to a mask mounting mechanism connected to the respiratory mask that prevents a portion of the attachment assembly and/or the straps from contacting the user's face, which provides additional convenience, ease-of-use, ease-of-adjustment, and improved comfort to the patient.
2. Description of the Related Art
It is well known to treat a medical disorder or to diagnose, treat, or monitor the condition of the patient using medical equipment. For example, a patient may be monitored and treated for various sleep disorders in a lab or in some other setting. An example of a type of sleep disorder is sleep apnea. Obstructive sleep apnea is characterized by the collapse of the upper airway during sleep, while central sleep apnea is characterized by the suspension of all respiratory movement. Obstructive sleep apnea and central sleep apnea may be combined in a condition referred to as mixed apnea.
In order to diagnose and/or treat such medical disorders, various equipment and devices are utilized. Further, there are numerous situations where it is necessary or desirable to deliver a flow of breathing gas, non-invasively, to the airway of a patient, i.e., without intubating the patient or surgically inserting a tracheotomy tube in their trachea. For example, it is known to ventilate a patient using a technique known as non-invasive ventilation. It is also known to deliver continuous positive airway pressure (CPAP) or variable airway pressure, which varies with the patient's respiratory cycle or a monitored condition of the patient, to treat a medical disorder, such as sleep apnea syndrome, in particular, obstructive sleep apnea (OSA), congestive heart failure, stroke, Cheynes-Stokes respiration, etc. Non-invasive ventilation and pressure support therapies involve the placement of a patient interface device, which is typically a nasal or nasal/oral mask, on the face of a patient to interface the ventilator or pressure support device with the airway of the patient, so that a flow of breathing gas can be delivered from the pressure/flow generating device to the airway of the patient.
A CPAP device delivers a flow of fluid to the airway of the patient throughout the patient's breathing cycle in order to “splint” the airway open, thereby preventing its collapse during sleep. In another type of treatment, bi-level positive pressure therapy is provided to the patient, in which the pressure of air delivered to the patient's airway varies or is synchronized with the patient's breathing cycle to maximize therapeutic effect and comfort to the patient. A pressure support device may also provide “bi-level” pressure support, in which a lower pressure is delivered to that patient during the patient's expiratory phase then during the inspiratory phase.
It is also known to provide an auto-titration positive pressure therapy in which the pressure provided to the patient changes based upon the detected conditions of the patient, such as whether the patient is snoring or experiencing an apnea, hypopnea, or upper airway resistance. Such a device adjusts the pressure delivered to the patient, based on whether or not the patient is snoring. For example, a pressure support device may actively test the patient's airway to determine whether obstruction, complete or partial, could occur and adjust the pressure output to avoid this result.
Other modes of providing positive pressure support to a patient are known. For example, a proportional assist ventilation mode of pressure support provides a positive pressure therapy in which the pressure of gas delivered to the patient varies with the patient's breathing effort to increase the comfort to the patient. Proportional positive airway pressure (PPAP) devices deliver breathing gas to the patient based on the flow generated by the patient.
For purposes of the present invention, the phrase “pressure support system”, “pressure support device”, or “positive pressure support” includes any medical device or method that delivers a flow of breathing gas to the airway of a patient, including a ventilator, CPAP, bi-level, PAV, PPAP, or auto-titration pressure support system.
Typically, gas such as oxygen or air is delivered by a pressure generating device, which may be, in turn, in fluid communication with an oxygen tank. The oxygen flows from the source through the regulator devices, through the pressure generating device and further through a conduit into a patient interface. The pressure generating device and the conduit, such as a gas hose, are considered the patient circuit. A coupling assembly is required for connecting the patient circuit to the patient interface device.
In a conventional pressure support system, a flexible conduit is coupled to an exit conduit from the pressure generating device. The flexible conduit forms part of the patient circuit that carries the flow of breathing gas from the pressure generating system to the patient interface device. In a support system, the patient interface device connects the patient circuit with the airway of the patient so that the elevated pressure gas flow is delivered to the patient's airway.
In order to provide gas or, as discussed above, oxygen, to a patient, the patient must use a patient interface device, such as a nasal mask (including external cushions and/or internal prongs), nasal/oral mask, full-face mask, nasal cannula, oral mouthpiece, tracheal tube, endotracheal tube, or hood. Typically patient interface devices include a shell having a cushion attached to the shell that contacts the surface of the patient. The shell and cushion are held in place by a headgear that wraps around the head of the patient. Together, the mask and headgear form the patient interface assembly. A typical mask attachment assembly includes headgear having flexible, adjustable straps that extend from the mask to attach the mask to the patient. Other techniques for attaching a patient interface device use a vice-like device that anchors at the front and back of the patient's head to support the mask on the user. See, e.g., U.S. Pat. No. 6,516,802.
Because such patient interface devices are typically worn for an extended period of time, a variety of concerns must be taken into consideration. For example, in providing CPAP or other positive pressure therapy to treat sleep disordered breathing, the patient normally wears the patient interface device all night long while he or she sleeps. In order to be successful in these applications, a patient interface needs to take into consideration two often competing goals: comfort and technical effectiveness. Failure to achieve either goal is likely to result in low efficacy. A comfortable, but technically ineffective, patient interface may achieve superior patient compliance; however, its technical ineffectiveness will minimize the therapeutic benefit achieved. Alternatively, a technically effective, but uncomfortable, patient interface may be capable of treating a patient; yet, the lack of comfort often results in low patient compliance. This also undermines the therapeutic benefit obtained by the patient. Thus, further advancements for interfacing a pressure support system to the airway of a patient are desired.
It is known to maintain such interface devices on the face of a patient by a headgear having upper and lower straps, each having opposite ends threaded through connecting elements provided on the opposite sides and top of the interface device, such as a mask. Because such masks are typically worn for an extended period of time, it is important that the headgear provides a sufficient seal against a patient's face without causing discomfort. One known headgear is disclosed in U.S. Pat. No. 5,517,986 to Starr et al. (“the '986 patent”) which has been assigned to the Assignee of the present invention and is hereby incorporated by reference. This headgear includes a headpiece 12 adapted to fit the crown and back of a patient's head. Lower straps 30 and 32 provide a two-point connection with a gas delivery mask 40. See FIG. 1 of the '986 patent. Depending straps 18 and 20, extending from headpiece 12, are connected to, and moveable relative to, the lower straps. Additionally, a pair of upper straps 56 and 58 can be used to provide a four-point connection with the gas delivery mask if needed as seen in FIG. 7 of the '986 patent.
As discussed above, adjustability of the mask and/or the headgear, together with increased patient comfort, is paramount; however, maintenance of the seal between the mask and the user's face must be adequately achieved. According to the prior art, various headgear have been developed that position the straps in various locations with respect to the mask in order to effect this seal. For example, in U.S. Pat. No. 6,470,886 to Jestrabek-Hart (“the '886 patent”), a clip 23 (FIGS. 14-16) or extender 20, 22 (FIGS. 8-11) is used to displace the bottom strap (or lip strap) of headgear down from the mask. However, the clips 23 or extenders 20, 22 of the '886 patent merely move the point of strap contact to a different position, namely just below the patient's lower lip. Although this effectively moves the contact point, this position may be incapable of providing either comfort or an effective seal. Locating the strap in this location may impede the user from moving their jaw or cause abrasion to the user's skin thus causing discomfort. In addition as the user movers their jaw, the straps may be biased in a manner that may result in reducing the effectiveness of the seal. Accordingly, the prior art headgear and masks still evidence contact between the strap (or extender and strap) and the patient's face. This configuration may result in devices that are perceived by the user as being unsightly, uncomfortable, and inconvenient to use. In addition, it is difficult to maintain an adequate seal in these devices.